What training classes and exercise are you doing with him? Honestly, he sounds like he's bored and trying to engage you in play.
They are a highly active breed, he sounds pretty normal for a GSD pup. Don't get frustrated with him, he's just a baby, I know it's hard to deal with them at that age sometimes, but you might try changing your routine up a bit to incorporate more training and something like nosework.
If he's not pottying outside, you need to go back to the basics with potty training and take him out more often, and praise like crazy when he goes outside.